A volunteer from the San Francisco Bicycle Coalition distributes the organization's Rules of the Road to cyclists commuting on Market Street in San Francisco, Calif. on Friday, April 6, 2012.

Photo: Paul Chinn, The Chronicle

A volunteer from the San Francisco Bicycle Coalition distributes...

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The first Critical Mass event, a citywide bicycle ride that takes place on the last Friday in cities around the world, occurred in 1992 in San Francisco with only a couple dozen bikers. These days Critical Mass averages about 1,000 riders.

The evolution of bicycle policy in San Francisco seems to be all about doing more to accommodate riders. It's time for City Hall to recognize that too many bicyclists are out of control - and more should be done to hold them accountable for rude, reckless and sometimes dangerous behavior.

The death of a pedestrian last week caused by a bike rider who reportedly ran a red light follows an earlier episode where another cyclist fatally injured a pedestrian. To be sure, the numbers of bike riders harmed by drivers outnumber these two incidents, and a weekend accident in Concord resulted in two deaths when an out-of-control SUV driver apparently jumped a sidewalk and struck a family out for a weekend ride.

Bike riders are a new ingredient in a crowded landscape. In the city, transportation officials and bike groups are pushing for more designated lanes, signals and warning signs that protect riders and alert drivers to the concept of sharing the road.

More education, information and - let's be clear - enforcement are needed to manage traffic in a congested landscape. Introducing a new concept such as widespread biking and the traffic rules that go with it will take a firm hand. Without such oversight, more injuries and fatalities will likely result.

The city's 13,000-member Bicycle Coalition insists that riders want to know their rights and responsibilities. Bike safety classes that once drew a dozen people now max out at 40 to 50 attendees. The group is meeting with police officials to spotlight the city's most dangerous intersections to cut down on accidents. These are both worthwhile directions at time when bike riding has grown by up to 71 percent in the past five years.

The learning curve for riders needs to continue. As the two fatalities show, bikes can be lethal. Steep drops on the city's hills can lead to unsafe speed, a possible factor in the recent fatality at the foot of the downhill stretch of Castro Street at Market. Bike brakes are nowhere near as reliable as those on cars or buses, making a quick stop nearly impossible. Riders who weave through traffic and shoot through stop signs and lights may be saving time, but they're adding to everyone's risk.

Cyclists need to examine their habits and conduct while demanding that drivers slow down and share lanes. Safety, respect and courtesy should be required for everyone on the road. Right now, that's not happening. Police need to step in and play a forceful role before further harm results.